Axial load ratio effect on wide-flange columns subjected to far field detonations

Abstract

A parametric numerical analysis was conducted to investigate the response of steel wide-flange sections (or I section) to combined axial and lateral far-field detonations upon their weak axis. Two steel sections, W150X24 and W200X71, were selected for this investigation. Utilizing ANSYS LS-DYNA as the Finite Element (FE) tool with a plastic kinematic material model, 30 simulations were carried out. These simulations involved varying the Axial Load Ratio (ALR) at 0 % (representing no axial load), 20 %, 40 %, 60 %, and 80 % under various blast impulses. The chosen material model accounted for strain rate effects and failure criterion. The numerical methodology was validated with two experimental cases, and their displacement plots were closely matched. The top of the column experienced a gradual linear axial load followed by a constant axial load, with a blast pressure applied. The study focused on parameters of maximum and residual axial load capacity, and maximum and residual displacement. The residual axial capacity assessment was performed by applying a slow linear axial loading rate to columns rested in their plastic deformed state. The significance of ALR was notable for the chosen quantities of interest. It was found from the simulations the noteworthy impact of ALR on the section's response to identical blast profiles, leading to scenarios of elastic behavior, plastic deformation, or failure. The Damage Index (DI) was calculated based on the residual to maximum axial capacity ratio, indicating the damage level of the column. Graphical representations between ALR and DI offer insights for building occupancy decisions and retrofitting options, crucial for preserving structural integrity.